Radio antenna apparatus



Dec. 26, 1950 L. HAMMOND RADIO ANTENNA APPARATUS Filed June 24, 1949 thus improve the picture.

Patented Dec. 26, 1950 UNITED STATES PATENT OFFICE I RADIO ANTENNA APPARATUS Chicago, I-ll.,- assignor to Hammond Instrument Company, Chicago, 111., a corporation of Delaware Application June 24, 1949, Serial No. 101,195

Laurens Hammond,

2 Glaims; 1

My invention relates generally to radio antennas and more particularly to means by which the position of an antenna may be remotely controlled.

In radio antennas for television reception, particularly in cities where the waves are absorbed and reflected by structures adjacent the antenna location, it is exceedingly difficult to position an antenna on the roof of a building so that it will pick up equally well the signals from a number of different transmitting stations.

In the past some alleviation of this difficulty has been accomplished by providing a remote control mechanismv by which the antenna could be rotated about a fixed vertical axis so that the best reception from each transmitting station could be found by trial. However, in many installations it is impossible, merely by changing the direction of the antenna, to secure satisfactory reception, free from ghosts. This is due to the fact that signals are received by different paths, by reflection from buildings, and the various paths have different lengths, causing a plurality of images which are displaced from one another on the viewing screen.

Sometimes it is possible, by merely rotating the antenna, to cancel an objectionable ghost, and A different ghost may nevertheless remain, and no further improvement may be possible; This different ghost may take the form of a positive or negative image, depending on the phase of the interfering signal, relative image. I have found that a further improvement can then be made by moving the center of the antenna in one direction or another such that the interfering image tends to pass from positive to negative, or vice versa, and at some position intermediate of the two, is thereby reduced in intensity so as to become unobjectionable.

It is not necessary that the person operating the receiver shall understand the theory, which is complicated, as the best picture is obtained by trial. Operating the controls while looking at the picture soon brings good results.

It is therefore an object of my invention to provide an improved radio antenna apparatus in which the antenna may be rotated in azimuth and in addition may be moved in a horizontal plane to a limited extent, thereby materially reducing the intensity of ghost images in a television receiver connected to the antenna.

A further object is to provide an improved antenna structure of the above described type which is remotely controlled and which may be easily 2 operated, is simple in construction, and be economically manufactured.

Other objects will appear from the following description, reference being had to the accompanying drawings in which:

Fig. 1 is a perspective view of the improved antenna structure and includes in a diagrammatic representation the remote controls for the operation of the antenna positioning apparatus; and

Fig. 2 is a schematic wiring diagram of the electrical parts of the apparatus.

Referring to Fig. 1, an antenna [6 is illustrated as being mounted upon a suitable mast H] which is secured to the building structure in a suitable manner, as by brackets I2. The antenna mast is preferably hollow so as to provide a conduit for the lead-in conductors, although this is not essential. The antenna i6 may be of any suitable construction but is illustrated as comprising a dipole l8 and a reflector 20" suitably secured to a cross bar 22 mounted on the end of a hollow shaft 24.

The hollow shaft 24 is driven by a motor mechanism 26, which may include any suitable revers ible driving motor and gearing connected to rotate the hollow shaft 24 through one complete revolution. The motor mechanism 26 is secured to the upper end of an arm 28 which is preferably hollow and has a vertically extending part 30 to which the motor structure 26 is suitably secured, a diagonal or horizontal portion 32, and a lower vertical end portion 34, the latter extending through a second motor drive mechanism 36 which is similar to the motor mechanism 26.

The motor mechanism 36 is suitably secured to the upper end of the mast H1 and the lower end portion of the hollow arm 34 extends through the motor mechanism 38 and is provided with a rotary and thrust bearing 38 carried by an arm 40 which is clamped to the mast 10. The coaxial lead-in conductor which is electricall connected to the antenna, extends downwardly through the hollow shaft 2 5 and has a portion 12 leading from the lower end of the shaft 24 into the hollow arm 28, extending downwardly through this arm and having a portion M which leads into the hollow mast [0. This coaxial cable extends from the lower end of the mast I0, as indicated at 36, and is connected to the radio or television receiver in the customary manner. In addition to the coaxial cable, suitable conductors connected to the motor mechanisms 26 and 36 also extend through the hollow arm 32 and the mast ID, these conductors being included in a cable 48 leading to a control box 50. This control box is provided with a pair of switch actuating knobs 52 and 53, the switch knob 52, when swung to the left rotating the motor 26 in a counterclockwise direction (plan View) while the switch knob 53 similarly controls the direction that the arm 28 is swung by the motor mechanism 36. A pair of indicator lamps 54 and 55, also mounted on the control box 50, indicate when the motors have rotated the hollow shaft 24 and the hollow arm 28, respectively through complete revolutions.

Circuits by which the motor mechanisms 26 and 36 may be controlled are schematically shown in Fig. 2, these circuits being illustrative of an other suitable control circuits. The motors of the motor mechanisms 26 and 36 are illustrated as being of the capacitor type, having rotors 56, and pairs of field windings 51 and 58. These rotors are mechanically connected to shift limit switches 59 and 60 to their full line positions upon completion of one revolution of the parts (24, 28) driven thereby, and to move the limit switches to their dotted line positions upon completion of one revolution of the driven parts in the opposite direction.

One end of each of the field windings 51, 58 is grounded while the other ends thereof are connected by a phase shifting capacitor 82, and are respectively connected to the poles of limit switches 59 and 60. The other poles of the limit switches are connected to the poles of motor reversing switch 66 and to the poles of signal lamp circuit reversing switch 68. The blade of switch 66 is directly connected to a low voltage current supply conductor Ill while the blade of switch 68 is connected to the conductor l through the lamp E5. The conductor Ill is connected to the ungrounded terminal of the secondary of a voltage reducing transformer T2, the primary being connected to an alternating current suppl line by a'main switch 14. The control circuits for the two motor mechanisms 25 and 36 are alike.

In adjusting the position of the antenna, the preferred procedure is as follows: After tuning the television or other receiver to the desired fre quency, the switch knob 53 is shifted to the left (L) or to the right (R) from is neutral (N) posi tion to cause energization of motor mechanism 26, and hence rotation of the antenna 16 about the axis of shaft 24, to a position in which the signal received is best. Under these conditions the television receiver may still display an objectionable ghost. If this is the case switch knobs 52 and 53 are moved in opposite directions, to L and R, or to R and L, at the same instant and both returned to neutral position at the instant the ghost image disappears or is of least intensity.

Since the motor mechanisms 26 and 36 are of the same construction, it will be apparent that as the antenna is swung in one direction about the axis of arm portion 34 by motor mechanism 3%, it is rotated about the axis of its shaft 24 in the opposite direction at the same angular speed. The antenna will therefore maintain the same direction but will be moved in a translatory manner. In this manner, the antenna may be moved toward or away from the maximum signa1 source, through a maximum distance of approximatel a quarter wave length, to a position in which the signal which caused the ghost image is in such phase with the main signal, as to eliminate the ghost image.

In some locations a number of ghost images may be present, but it has been found that by operating the apparatus in the manner described, an antenna position can be found in which all ghost images are eliminated, or their intensity so greatly reduced that they are not seriously objectionable.

While I have shown and described particular embodiments of my invention, it will be apparent to those skilled in the art that numerous modifications and variations may be made in the form and construction thereof, without departing from the more fundamental principles of the invention. I therefore desire, by the following claims, to include Within the scope of m invention all such similar and modified forms of the apparatus disclosed, by which substantially the results of the invention may be obtained by substantially the same or equivalent means.

I claim:

1. An antenna structure for high frequency radio receivers comprising a support, an arm extending from said support in a direction having a substantial horizontal component, a first reversible motor carried by said support and connected to said arm to swing the latter about a vertical axis through substantially one complete revolution, an antenna, a second reversibl motor secured to the outer end of said arm and connected to the antenna to rotate the latter about a vertical axis, and manually operable remote switch means to control the operation of. said motors, whereb the antenna may be oriented by operation of either motor and may be moved in a translatory manner by simultaneous operation of both of said motors in opposite directions at the same speed.

2. An antenna structure for high frequency radio receivers comprising a support, an arm extending from said support in a direction having a substantial horizontal component, a first reversible motor mechanism connected to said support and to'said arm to swing the latter about a vertical axis, an antenna, a second reversible motor mechanism secured to'the outer end of said arm and connected to the antenna to rotate the latter about a vertical axis, and manually operable remote switch means to control the operation of said motorl mechanisms, whereby the antenna may be oriented by operation of either motor mechanism and may be moved in a translatory. manner by simultaneous operation of both of said motor mechanisms in opposite directions at the same speed.

LAURENS HAMMOND.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS page 80. 

